Acoustic signaling device



' July 28, 1925.

G. H. SCHIEFERSTEIN ACOUSTIC SIGNALING DEVICE 3 Sh eets-Shaat l 7 File March 17 l i .J

July 28, 1925. 1,547,527

a. H. SCHIEFERSTEIN ACOUSTIC SIGNALING DEVICE Filed March 17, 1924 3 Sheets-Sheet 2 3 Sheets-Sheet 3 July 28, 1, 925.

G. H. SCHIEFERSTEiN ACOUSTIC S IGNALING DEVICE Filed March 17, 1924 Patented July 28, 1925.

UNITED: STAT ES PATENT' OF'FlClE;

GEORG HEirinIo'H scnmmasmm, on BER-LiN-CHARLOTTENBURG, GERMANY- Aoocs'rro SIGNALING DEVICE.

Application filed March 17, 1924., Serial No. 699,808.

My invention relates to acoustic signaling devices; more especially, it'relates to. motorcar horns, sirens, and the like. Ofthe-v motor-car hornsthe oldest. and most widely knownconstruction is basedon ,the ,pri n ciple of the reed-pipe in which an air-passage: is alternately throttled or opened .by the oscillating reed. Horns of this ,kind are actuated generallymanually with the aidof 'a; rubber-ball The. driver must, therefore, remove his hand from the steer ing-wheel which is felt a disagreeable interrcpt-ion; In view of thistherewas. intro duced some, time latera plurality of I, sound. producing devices which were capable. of being operated by a.push-button arranged incertain cases on the steeringwheel. lhe sound-producing devices or; horns of this kind were electrically operated, and based in most cases on the principleofthe make.

and-break contacts. A drawbaclt connected with devices of this kind consists 111 the wear and tear of the malte-and-break contacts,.as well as in the thereby produced alteration of the sound. These detrimental effects gave rise, of late, to the introduction of the motor horn proper in which the diaphragm is caused to oscillate by positively or compulsorily acting means. The sound produced in this Way is loud, it is true, but very impure.

My invention is based on another idea which consists in producing a loudand harmonic sound bynieans of mechanically oscillating tuned and loosely coupled arrangements and combinations, or systems, of parts forming mechanisms free from the drawbacks mentioned.

The invention is illustrated byway 'of example. in the accompany ng drawings in Figure l'is, in diagrammatical representation, in .plan of a sound-producing device constructed according to my invention, some parts being merely indicated by dotted lines;

Figure2 is a side view of the same device, the sound-producing device proper, in

the righthand half of the figure, being shown in vertical section;

Fig. 2 is an elevation of the diaphragm, Figure 3 is an illustrationsimilar to Fig; ure 1, but showing a modification; Figure l is a side View of another modifi cation, r

Figure 5 is an axial sectionof. a sound-v boX for use in connection with my invention; and

Figure 6 is a side-view, of this, sound box, in connection withcertainother parts,

all being duly described, in. detail herein,- aften.

Fig. 7 is a longitudinal sectionof anace tual construction, and v Fig. 8 is avertical.sectionthereoi' through the driving shaft showing the; diaphragm in elevation. 3

ReferringtoFigures 1. and 2, and,assum;. ing the diaphragm bof amotor-car, horn or the like to be a mechanical oscillatory. system which is, .in this case, loaded .withlaj bow a, thissyStemcan, in View of. experi;

ences gathered. lately by the department of mechanical; oscillations, be, excitd from without by means of a, loose couplingand can be caused to oscillate energetically and Y to produce sounds after having been tuned appropriately. v i 1 The sounding of the device is obtained in Figure l by causing the rotary body supported in the bow .a on apine to rptate, the rotation being, effected. bythe e lectio motor m, its pulley n, and rubber 7a, The rotary body consistsoif asmall,cordj ulley k? and of two small, eccentricallyarranged weights 70 and these latter cause the ,diaphragm to bend alternately tooneband the other side during each oscillation, according to the freeness thereof i. e., whether ',;its

central-actuating pin is rigidlylor. loosely,

connected thereto. The power requisite to obtain the acoustic efiect is,,,thus, in the example. in question, transmitted. by a true masscoupling, As the number of revolu'; tlons of themotor' amounts to from 2090. to

300i), the ratio o t-the transmission canpbe chosen between ,wide limits, and it is ren -f dered possible thereby, to produce olesired oscillation 'falling within the tone;

scale. The use of a rubber-belt as, power transmitting means has proved especially advantageous as it does not damp perceptibly the oscillations of the diaphragm. An extraordinarily, high percentage of the motor-output can, therefore, oscillatory energy.

be converted into Horns of this kind permit a range over a large part of the tone-scale, irrespective of tions of the diaphragm; The pitch of the tone alters, of course, with the number of revolutions of the motor, and is,therefore, lower at starting than later on when the motor has'attained its proper or normal Working speed.

If it is intended to cause the tone' to pass over a large part'of the'scale similarly to a siren,'that can be attained easily by providing the motor with a heavy fly-wheel (large moment of inertia). If, on the other hand-'- what might be'desir'able 'as'"regards motorcar horns-only slight, alterationsof :the tone'while themotor proceeds from starting to the service-number of revolutions shall take place, then the inertia of the motorarmature must, reversely, be chosen as small as possible. The effect in question can,-

however, also be attained in a certain measure by means of anoscillatory system with but slight damping (intermediate system) which is inserted between the other members, as is explained hereinafter. fl H I now refer to Figure 2 in which the oscillatory "system which consists of the diaphragm b and the mass a aflixed thereto is combined with another oscillatory system which consists of flat springs b" and weights a affixed to the ends thereof, and the damping of which is only slight. This additional oscillatory system takes up only little energy at the commencement of an oscillation, but a relatively large amount of energy in the form of oscillations when the reso nance position has been reached, whereby quick rise up to the service-number (resonance-number) of the revolutions is promoted, and there arises, besides, with pure tuning proportions, a relatively undamped pure tone by said intermediate system. The diaphragm can, under circumstances, be so chosen in this case thatits natural period falls quite outside the service-number of revolutions, that is to say, that it can be regarded merely as a member delivering useful lamping. In order to reduce losses still more, or, in other words, to increase the eiiiciency of the entire arrangement, the column of air vibrating in the sound-tube can be tuned in agreement with the pitch of the tone produced, that is to say, with -the number of periods.

If, instead of one mass, such as k is,

areemployed, perhaps three, as in Figure 3 (where there are threecord-pulleys n n n and three rotary masses 7c 70 as well as three intermediate systems a b, a harmonically sounding accord can be produced for instancewith a'ratio of 1:3/212.

Either in connection with this arrangement (Fig. 3) or separately, a system of resonators devised, for instance, according to Figure 4, can be used. The sound wave to be produced at the point 0 is here conducted by the tube 1 (which can be tuned according to the respective sound, or behaves aperiodically with respect thereto) and thence into the tube 2 which is so shaped as to form a resonator and may be so devised as to permit alterations of its length at its free end in order to allow of an accurate adjustment. The tube 1 terminates into the tube 2 near the place of the oscillation loop of the air-column, that is to say, at that place where the air motion is greatest. If the tube 2 is shifted on the tube 1,-that is to say, if the degree of coupling is increased or decreased, the influence of the air column in the ,tube 1 on the air-column in the tube 2, that is to say, the degree of coupling, can be increased or decreased. The ratio between the tube or resonator 2 and the tube 1 is the same as that between the tube or resonator 3 and the tube or resonator 2.

The righthand part of the Figure 4 shows, thus, a device by means of which any desired number of accurately determined overtones can be derived from any desired fundamental tone. The possibility to obtain pure oscillations which can be augmented to a full-sounding accord places horns of this improved kind ahead of all other ones which have become known up to now.

Putting the endless rubber belts onto the cord-pulleys or exchanging them 3), can be effected without any dismounting ef any part as the member or bow w is overhanging.

The subject natter of the invention is not changed if instead of a mass-coupling (Figs. 143) any other type of coupling, for instance an elastic coupling with crankdrive, is employed. An example of such a coupling and drive is illustrated in Figure 4:, the middle part of which shows the elastic coupling and the lefthand part of which provided with a pin .9 co-operating' with the counter-part O secured to the diaphragm 'b in the centre thereof. The diaphragm b may oscillate periodically or'aperiodically, as the case may be. The rotary member ir 11: (Figs. 1 and or the rotary members k 70 (Fig. 3) need not at any rate be actuated by an electromotor or the like, but any other driving means, also manually actuated driving, such, for instance, as ahandcrank or the like, may be used. In the ex ample shown in the lefthand part of the Figure 4: it is assumed that the cord-disk n is driven from a crank-actuated shaft n by the intermediary of two smaller cordpulleys a 12. and another endless cord a In the example illustrated in Figure 4 the cord-pulley it drives a crooked shaft m supported in bearings m by means of an endless cord 1' and a small cord-roll 70, and the crooked part of said shaft is connected by a rod m with one leg of the tuning fork 7: whereby this latter is caused to vibrate, the vibrations being then transmitted to the pin 3.

lVith every mechanism intended to produce pure acoustic oscillations the soundproducing member must be able to perform free vibrations, that is to say, it should not be impeded as regards its amplitude. If, thus, a pure tone is to be produced, it if necessary to provide, between the driving and the driven oscillating member, means permitting unimpeded vibration of the sound-producing member. The above-mentioned rubber-belt has proved to be a transmitting member of such a kind.

YVhile on the preceding pages means have been disclosed capable of producing, by direct excitation of an oscillatory system in the form of a diaphragm, sound suited for signals given by horns or sirens, I will now describe modifications by which sounds ca pable of covering considerably longer dis tances can be produced. This increased effect is based on this development of the general idea of the invention that the elastic part, the. diaphragm, is loosely connected with the oscillating mass of the oscillatory system in such a manner that prior to every reversal of the motion a small relative shifting between said two members takes place, the extent of this shifting between O and its actuator is a few millimeters, so that, so to speak, a constant hammering takes place between the mass and the diaphragm,

or diaphragms, in its, or their, oscillating state. In this way a large number of considerably energetic over-oscillations capable of carrying the sound over a long distance and to make it piercing are produced.

Another discovery resides therein that the thus produced over-tones are kept up best by sound-producing devices devised as radiators, that is to say, devices radiating the sound to two sides without the co-operation of a trumpet.

in the example illustrated in .Figuret, b b are two diaphragms between which a mass a is so affixed that some play remains at the fastening points 0 0, the play depending in some measure on the size of the diaphragm and amounting, perhaps to fractions of a millimeter. The two diaphragms b Z3 which may be undulated inorder to have a greater amplitude, and the casing cl, to the two frontal sides of which the dia phragms are attached, form a completely closed chamber y, The air enclosed in this chamber and contacting with the inner surfaces of the diaphragms is thereby caused to vibrate, whereas the outer surfaces of the diaphragms produce efiicacious' sound waves;

Within the chamber 3 the rotary mass k is supported on a short spindle 2 carried by the connecting member a of the diaphragms b 6 and is rotated by any source of energy, for instance by an electromotor M, the motion being transmitted to the rotary mass 73 by a belt or cord, preferably a rubber cord 1*. In the example illustrated the motor M is housed within the chamber y, but the spindle a may be a shaft which extends to the outside of the casing d and the motor may be arranged outside thereof. Also the fly-wheel of the car-motor may be used as driving means for the rotary mass 10 An arrangement of this kind is shown in Figure 6.

D is a sound-radiator of the kind shown in Figure 5, and W is a flexible shaft connected (by means hereinafter described) at one end with the rotary mass 70 and provided at the other end with a friction disk F which is supported in a forked upper end of a supporting member G carried by pivots Z Z and being connected at its lower arm H with a BOWCl611C2Lbl6 by which the disk F can be moved against the circumferential surface of a rotating disk or fly-wheel, for instance that of the car-motor, so that the disk F is then rotated by the friction arising bet-ween itself and the disk or fly-wheel S; If the number of revolutions of the motor is variable, first the disk F will, owing to the oscillatory system being controllable, assume a number of revoluations corresponding to the resonance number of revolutions and its slip will then increase more and more relatively to the disk or fiy-wheel S. In order to prevent the disk F, at a very high number of revolutions, from rotating with a number of revolutions causing surpassing of the resonance number of revolutions, it may be provided with an elastic or rubbing means, that is to say, it may be combined, for instance, with a friction-clutch, for instance of the kind shown" at K in Figure 6.

without specially additional or supplementary means, a variation of the number of revolutions entails, it is true, a variation of the sound, so that the purpose of the device, via, giving signals, can be attained in all cases also with a variable number of oscilla tions and the sound produced varies.

By providing one or more tuned additional systems which can also be housed in the chamber 3 between the diaphragms, or by using tuned air-columns, trumpets, or the like, a definite natural oscillation can be impressed also onto modifications of the kind illustrated in Figures 5 and 6 of a definite characteristic respectively. If a definite characteristic shall be impressed on to the radiated sound waves, for instance in such a manner that the over-oscillations are caused to remain more in the rear, a soundbox of the kind shown in Figure 5 may be provided with one or more trumpets, for instance as T and T in Figure 6 (indicated only by dotted lines), and any one or both may be rotary, as indicated with respect to the upper trumpet T In Figs. 7 and 8 I have illustrated a construction comprising a casing consisting of a conical front member having a central tube 1 and additional concentric tubes 2 and 3, as indicated in Fig; 4 A frame (Z is secured thereto, and to the frame is secured a sheet metal cover 0 which is also connected. to the member 1 as shown. Between the frame d and member 1 is secured at its edges an undulated circular diaphragm 25 A yielding, flexible plate 72 which is preferably but not necessarily a second diaphragm, is mounted on the frame d. The oscillator a is mounted on this plate and has a yoke a that sup-ports the shaft or pin on which the actuators or weights 0 and 76 are loosely mounted. These weights are rotated on the pin a by round rubber belts r and r that pass over cord pulleys n and a The flexible plate or diaphragm Z2 may be substituted by another undulated diaphragm as in Fig. 5, of the same dimensions as the diaphragm 6 The pulleys, here shown as made in one piece, are mounted on a shaft to driven by a flexible shaft 10 or otherwise, through the medium of a friction clutch R, R.

A bolt 3 passes through the center of the diaphragm 72 into the oscillator a. The bolt in this instance is shown as not clamping the diaphragm tightly and the diaphragm is free to move slightly with respect to this bolt. This permits a sharper tone. This bolt, however, may be screwed into the oscillator to tightly clamp the diaphragm to the oscillator to lower the tone.

a are the weights adjustably connected for tuning purposes to the ends of. the leaf springs Z) secured in or cast in the oscilla tor a and constitute the intermediate systern.

By rotating the eccentric weights is and 76 the oscillator a is set in vibration, which vibration is permitted by its supporting leaf spring 72 The intermediatesystem a, b relatively undamped assists the maintenance of this oscillation, and the diaphragm follows it, being urged to vibrate by contact alternately with the head or bolt 1 and with the adjacent end of the oscillator, there being a limited free movement between the diaphragm and oscillator by reason of the loose connection or coupling between the diaphragm 7)2 and oscillator a.

I claim:

1. An acoustic signal, comprising a sound producing member, an oscillatable coupling element having an appreciable mass loosely connected to said member, a source of energy, an oscillator mounted on said coupling element and a yielding mechanical element transmitting energy from said source to said oscillator element and causing the 0s cillation thereof.

2. An acoustic signal, comprising a vibrating sound producing member, an osci1- lating coupling element loose with respect to said member to permit independent vibration of said element within small limits, a source of energy, a rotatable oscillator mounted on said element and a yielding mechanical element operated by the source of energy to rotate said oscillator and set the coupling element in oscillation.

3. In an acoustic signal, a sound producing member, an element loosely connected to said member to vibrate the same, means to oscillate the element, and separate vibrating means mounted on said element and capable of independent vibration.

L. In an acoustic signal, the combination with a sound producing member, of an element loosely connected to said member, a plurality of substantially undamped mechanical oscillating devices mounted on said element and a source of energy from which said oscillating devices are actuated.

5. In an acoustic signal, the combination with a sound producing member; of a yielding mechanical coupling device, a yielding mechanical member supported by and mounted on said coupling device, and means to operate said member to set up oscillations in said coupling device, said coupling device arranged to transmit oscillations to said member.

6. In an acoustic signal, the combination With a sound producing diaphragm; of a mechanical coupling member, loosely connected to said diaphragm, a mechanically operated element supported by and mounted on said coupling member, and a source of energy for driving said element, said element being operated from said source to set up oscillations in said coupling member substantially in tune With the oscillations of said diaphragm.

7. In an acoustic signal, the combination with a diaphragm;- of means for oscillating said diaphragm, a tuning device mounted on said means, a mechanical device for actuating the diaphragm actuating means, and means to drive said device and thereby actuate the diaphragm actuating means under the control of said tuning device.

8. In an acoustic signal, the combination With a sound producing member; of a mechanical coupling device arranged to transmit movement thereto, a rotary oscillator mounted on said device, a source of energy, and a yielding mechanical element connecting said oscillator to said source of energy to rotate the oscillator and actuate said device to vibrate said member.

9. In an acoustic signal, the combinationwith a sound producing diaphragm; of an oscillating coupling device loosely connected thereto, an eccentrically Weighted rotary member mounted on said device, a motor, and a flexible driving connection between said motor and member.

10. In an acoustic signal, the combination With a sound producing diaphragm; of an oscillating coupling element, a shaft mounted between the end of said member and the element, a plurality of belt pulleys on said shaft, eccentric Weights carried by said pulleys, a motor, and endless driving belts connecting the motor and pulleys.

11. In an acoustic signal, the combina tion With a diaphragm; of a coupling member mounted for oscillation and loosely connected to said diaphragm for limited inde pendent movement, a plurality of separately rotatable masses mounted in said member, and means for driving said masses.

12. In an acoustic signal, the combination With a diaphragm; of a member to oscillate said diaphragm, means to set said member in oscillation and means to tune said member With respect to said diaphragm, said means mounted on and carried by said member.

13. In an acoustic signal, the combination with a diaphragm; of a member to oscillate the diaphragm, a plurality of separate tuning means mounted on said member and means to oscillate the member.

14. In an acoustic signal, the combination with a diaphragm; of a member to oscillate said diaphragm, an oscillating device rotat ably mounted on said. member, means to drive said device and thereby oscillate said member, and a plurality of tuningelements mounted on said member and adjustable for resonance.

15. In an acoustic signal, the combination with a sound producing element; of a mem her to oscillate said element, a plurality of tuning elements rigidly. connected to said member and having different harmonic effects, an eccentric rotating means on said member for oscillating the member and means to yieldingly drive said means.

16. In an acoustic signal, the combination with a sound producing member; of a coupling device loose with respect to said memher, a plurality of elements for actuating said device, means to separately drive said elements, a plurality of springs rigidly secured to said device, means to adjust the vibration of said springs and means to loosely connect said device and member.

17 In an acoustic signal, the combination With a diaphragm; of a coupling comprising a yieldingly supported. device, means to loosely connect said device With said diaphragm, a plurality of differently proportioned movable Weights mounted in said device, a motor, means to yieldingly actuate said Weights from said motor, a plurality of tuning devices connected to said device and means to adjust said devices.

18. In an acoustic signal, the combination with a plurality of sound producing members; of a coupling device loosely connected to and supported by said members, a movable Weight mounted in said device, and means to actuate said Weight to oscillate said device and thereby actuate the sound producing members.

19. In an acoustic signal, the combination with a plurality of diaphragms; of a coupling device loosely connected to said diaphragms, a rotatable Weight supported by said device, a motor, and a belt between the motor and Weight for driving the latter.

20. In an acoustic signal, the combination with a plurality of diaphragms; of a coupling device loosely connected to said diaphragms, a rotatable Weight mounted in said device, a tuning element secured to said device, a motor, and a belt connecting the motor and Weight to rotate the same.

21. In an acoustic signal, the combination with a plurality of diaphragms; of a coupling device connected thereto, a plurality of separately rotatable Weights mounted in said device, a motor, and driving belts between the motor and weights.

22. In an acoustic signal, the combination with a plurality of diaphragms; of a coupling device loosely connected to said diaphragms, a plurality of separate rotary Weights mounted in said device, a plurality of tuning members connected to said device,

a motor, and flexible means between the motor and weights to drive the same.

23. In an acoustic signal, the combination with a plurality of diaphragms; of .a coupling device connected loosely to said diaphragms, a plurality of separate rotary weights mounted in said device, a plurality of tuning elements connected to said device, means to tune said elements, a motor and a flexible driving means between said motor and weights.

24. In an acoustic signal, the combination with a pair of diaphragms; of a coupling device comprising a weight connected to the diaphragms between them, a yoke on said device, a shaft mounted in one end of the yoke and in said device, a. pair of rotary eccentric weights mounted on said shafts, leaf springs rigidly connected to and extending from said device, weights adjustable along said springs, a motor, and a flexible driving means between said motor and weights.

25. An acoustic signaling device, comprising, in combination: a diaphragm, a loose mechanical coupling connected with said diaphragm and some play being left at the point of connection, a rotary eccentric mass supported in said coupling, a source of energy, a shaft so arranged as to be adapted to transmit rotary motion from said source of energy to said rotary mass, and a friction clutch inserted between the said source and the said shaft, substantially as set forth.

26. An acoustic signaling device, comprising, in combination: a diaphragm, a loose mechanical coupling connected with said diaphragm and some play being left at the point of connection, a rotary eccentric mass supported in said coupling, a source of energy and a flexible shaft so arranged as to be adapted to transmit rotary motion from said source of energy to said rotary mass. the said source of energy being separated from the sound-producing means, substantially as set forth.

In testimony whereof I affix my signature in presence of two witnesses.

GEORG HEINRICH SCHIEFERSTEIN.

\Vitnesses:

EGoN A. WnN'rznL, KARL TH. D. MANN. 

